Due to the endogenous automictic nuclear behavior of the cultivated mushroom as described by Kerrigan in Evolution and Agaricus bisporus, Ph.D. disseration (1989), University of California (Santa Barbara), few new and unique varieties of cultivated mushroom have become commercially available. Those that have become available and that have been used commercially were developed primarily to achieve high production yields and a bright, white color. As a result, nearly all commercially produced mushrooms are genetically very similar as described by Royce and May in Mycologia 74:93-102 (1982).
A consequence of the genetic similarity of most commercially-produced mushrooms is that they are susceptible to diseases caused by common pathogens. The diseases can have a devastating impact on the yield and quality of a mushroom harvest. Verticillium disease, also called dry bubble and Verticillium spot, is one of the most troublesome of these diseases. It is caused by the fungus Verticillium fungicola (Preuss) Hassebr. var. fungicola as described by Gams and Zaaryen, Neth. J. Pl. Path. 88:57-58 (1982).
Typically, Verticillium disease is controlled with hygienic cultural practices and/or fungicides. Currently, the most effective commercial fungicide approved and labeled for such control is zinc ethylene bisdithiocarbamate known to the trade as Zineb.TM.. However, the Environmental Protection Administration has suspended its approval for the registration of this material, and it can no longer be used in the United States. Without it, many mushroom farms using conventional mushroom varieties will most likely not be able to sustain the yield and quality levels which they need to remain economically viable.
Consequently, the incorporation of disease resistance into the genetic makeup of mushroom varieties represents an efficient, cost-effective and environmentally responsible solution to the problem, and a need for such a disease resistant mushroom exists.